This invention relates generally to a torquelimiting clutch. More particularly, it relates to a torque-limiting clutch which includes a mechanism to effect rapid clutch release upon the sensing of a relatively low excessive temperature so as to reduce slipping and prevent clutch destruction or more extensive damage to associated equipment.
It is well known in the prior art to provide a gear, chain or belt drive train, for example, to couple a source of input torque with an output which drives associated equipment. Often a torque-limiting clutch is included to protect such equipment by disengaging the drive train when it is overloaded. In the event torque transferred through the drive train increases due to overloading, jamming, etc., the clutch friction elements slip, thereby producing wear and destructive heat.
The typical temperature-responsive torque-limiting clutch tends to disengage when this occurs. It usually includes a temperature-responsive bimetallic spring to separate the friction elements in response to the sensing of an excessive temperature. However, a bimetallic spring generally deforms slowly in response to temperature changes through a wide temperature range. As a result, separation of the friction elements takes place at a relatively high temperature, for example above 300.degree. F. The friction elements continue to slip during the transient period in which the bimetallic spring deforms. Indeed, slippage increases during this transition, producing additional wear and heat. Further, the torque setting of the cluch decreases as the bimetallic spring force increasingly opposes the force tending to keep the clutch engaged.
There is a need in the art for a torque-limiting clutch including a temperature-responsive release mechanism which will rapidly effect clutch disengagement when a relatively low excessive temperature is sensed. Rapid disengagement at a low temperature minimizes wear, heat damage and changes in the torque setting, thereby protecting the clutch and associated equipment.
In addition, it is often necessary to use a torquelimiting clutch in an environment where space limitations are severe. The use of a bimetallic spring in such an environment often presents a problem, because the spring must be relatively large to insure that sufficient clutch-disengaging force is developed. Thus, there also is a need in the art to provide a torquelimiting clutch in a small package.
Further, it would be a desirable feature for such a clutch to have the capability either of cycling to re-engage when the temperature drops or of remaining disengaged, as desired.